The present invention relates to improvements in grates for furnaces, especially for large industrial furnaces, and more particularly to improvements in means for mounting grate bars in or on the frame of a grate, particularly a grate which is movable by mechanical means in a furnace or the like. Still more particularly, the invention relates to improvements in grates of the type wherein one end portion of each grate bar engages with a portion of the frame and another portion of each grate is coupled with the neighboring grate or grates in such a way that the other portion cannot be shifted at right angles to the general plane of the assembled grate bars. The other portion of each grate bar may constitute the other end portion or an intermediate portion of the respective grate.
The bars of a grate must be separated from each other by clearances or gaps in order to allow for heat-induced expansion as well as to permit oxygen-containing gases to contact, from below, the layer of burning fuel on the grate. Fragments of burning fuel invariably penetrate into the aforementioned clearances and tend to increase the distance between neighboring grate bars. Shifting of one or more grate bars from their normal positions can entail jamming of an entire series or row of bars and/or lifting of one or more bars to a level above the remaining components of the respective section of the grate.
Attempts to prevent lifting of grate bars include the provision of one or more lateral protuberances which extend from the grate bars and into openings of the neighboring grate bars or are disposed below suitably configurated ribs of neighboring bars. Such protuberances connect the grate bars to each other against upward movement (i.e., at right angles to the general plane of the grate) and/or against movements of discrete grate bars in the direction of movement of the entire grate. Sidewise shifting of neighboring grate bars with respect to each other is prevented or impeded by the provision of lateral blocking plates. In accordance with a further known proposal which is disclosed in German Pat. No. 911,317, neighboring grate bars are connected to each other by hook-shaped coupling elements which hold such bars against upward movement as well as against sidewise movement relative to each other. The hook-shaped coupling elements can extend into elongated openings of neighboring grate bars so as to enable the bars to move lengthwise to the extent which is determined by the length of openings. Such movements are desirable or necessary in order to allow for convenient cleaning of the grate, i.e., for expulsion of fragments of fuel and/or solid combustion products from the aforementioned clearances. In such instances, alternate grate bars are fixedly mounted in the frame of the grate and the remaining bars are movable lengthwise of the fixedly mounted bars. FNT *The German Patent No. 911,317 fully discloses the means for moving every second row of grate bars.
When solid particles of foreign matter penetrate between and prevent relative movement of certain grate bars or of each and every bar, the ends of mobile bars are likely to be lifted off the frame because such ends merely rest on the adjacent portions of the frame. Since the coupling elements for neighboring bars are disposed in the front or median portions of the bars (as mentioned above, such elements normally prevent upward movements and, in some instances, also lengthwise movements of neighboring bars relative to each other), the foreign particles are likely to produce a shear effect, i.e., at least one of two neighboring grate bars pivots with respect to the other bar not unlike one half of a shears. The pivot axis for such movement is defined by the coupling elements. This causes those end portions of grate bars which are remote from the points of connection to the frame to rise above and away from the grate bars therebelow. As a grate bar pivots relative to the neighboring bar, the width of the clearance therebetween increases whereby the clearance is even more likely to receive one or more large particles of solid foreign matter to prevent pivotal movement of the displaced bar back to its original position. This prevents or interferes with orderly operation of the corresponding stage of the grate, i.e., the stage or section is likely to jam and/or to undergo minor or major physical damage including total destruction.